Since the oil crisis of the early 1970s, there have been an increasing demand for smaller, more fuel efficient cars. Automotive manufacturers in the United States have responded to this demand by introducing vehicles powered by four-cylinder engines of recent design. These new designs represent the considerable investment in design, development, and manufacturing facilities on the part of the automobile manufacturers and their suppliers. These increased costs can only be recovered by passing them on to the consumer.
The smaller vehicles must be designed with smaller engine compartments which cannot accommodate the six and eight-cylinder engines commonly produced by the United States auto industry during the last 40 years. The engine families developed for the smaller vehicles are often completely new designs which are inherently costly. In order to satisfy customer performance expectations, manufacturers have increased engine displacement, but with increased displacement, four-cylinder engines have harsh vibration characteristics. The current practice is to dampen these vibration characteristics with the addition of counter rotating, balancing shafts, but these shafts increase the weight of the engine, increase the cost of production, and consume some energy in their operation which greatly compromise the value of the four-cylinder design. The other alternative, a small displacement 60-degree V-6 engine, is an even more costly solution.
Under the current method for balancing engine crankshafts, the requirement is to first statically balance the crankshaft, without accounting for the weight of the piston and connecting rod assembly, prior to dynamically balancing the crankshaft thereby placing an upper limit of 2,000 cubic centimeters on the total displacement of four-cylinder engines. The economic inherent in producing a truly large displacement four or even two-cylinder engine has been regarded as impossible or impractical to achieve utilizing current balancing procedures.